Jones defeated Daniel Cormier by TKO via a head kick for the title at UFC 214 on July 29, 2017. Shortly after the bout, he called out reigning WWE Universal Champion Brock Lesnar.

UFC President Dana White confirmed to ESPN that Jones failed a drug test in connection with his fight but clarified that he has not been formally stripped of his title. If the results hold, according to ESPN, that would be the expectation. TMZ Sports reported the belt would go back to Daniel Cormier.

Some fans were hoping Lesnar would return to MMA to face Jon Jones in a UFC super-fight pitting two of the world's best heavyweights against one another. Brock, however, has his own issues with failed drug tests as he would be unable to return to the Octagon until he finished serving out a one-year suspension for failed drug tests in conjunction with his UFC 200 fight against Mark Hunt. When Lesnar retired from MMA, his suspension was frozen. He must be back in the testing pool for a full four months before he's able to fight. Last time he fought he was granted a testing exemption, which resulted in two failed drug tests, a suspension and a civil lawsuit filed by his opponent.

This is Jones's second failed USADA drug test, as he tested positive for two banned substances, Hydroxy-clomiphene, an anti-estrogenic agent, as well the Letrozole metabolite, an aromatase inhibitor, prior to his UFC 200 against Daniel Cormier in out of competition tests. He was removed from the card and served a one-year suspension. Cormier went on to fight Anderson Silva, a fight he won by unanimous decision.

Jones blamed those positive tests on a male enhancement pill, which he didn't realize contained a banned substance.

TMZ Sports reports Jones faces a ban of up to four years, essentially ruling out a fight with Lesnar. The UFC issued the following statement:

The UFC organization was notified today that the U.S. Anti-Doping Agency (USADA) has informed Jon Jones of a potential Anti-Doping Policy violation stemming from an in-competition sample collected following his weigh-in on July 28, 2017.

USADA, the independent administrator of the UFC Anti-Doping Policy, will handle the results management and appropriate adjudication of this case involving Jones, as it relates to the UFC Anti-Doping Policy and future UFC participation. Under the UFC Anti-Doping Policy, there is a full and fair legal process that is afforded to all athletes before any sanctions are imposed. The California State Athletic Commission (CSAC) also retains jurisdiction over this matter as the sample collection was performed the day before Jones' bout at UFC 214 in Anaheim, CA, and USADA will work to ensure that the CSAC has the necessary information to determine its proper judgment of Jones' potential anti-doping violation.

Additional information will be provided at the appropriate time as the process moves forward.